Light Reflection and Refraction Test

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Light Reflection and Refraction Test - 67

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Weekly Quiz Competition

Question 1
1 / -0

A point object is placed at a distance of $$10\ cm$$ and is real image is formed at a distance of $$20\ cm$$ from a concave mirror. If the object is moved by $$0.1\ cm$$ toward the mirror, the image will shift by about

A
$$0.4\ cm$$ away from the mirror

B
$$0.4\ cm$$ towards the mirror

C
$$0.8\ cm$$ away from the mirror

D
$$0.8\ cm$$ towards the mirror

Solution

Mirror formula
$$\dfrac{1}{f}=\dfrac{1}{v}+\dfrac{1}{u}\Rightarrow \dfrac{1}{f}=\dfrac{1}{-20}+\dfrac{1}{(-10)}\Rightarrow f=\dfrac{20}{3}\ cm.$$ If object moves towards the mirror by $$0.1\ cm$$ then.
$$(10-0.1)=9.9\ cm.$$ Hence again from mirror formula $$\dfrac{1}{-20/3}=\dfrac{1}{v'}+\dfrac{1}{-9.9}\Rightarrow v'=20.4\ cm$$ i.e. image shifts away from the mirror by $$0.4\ cm.$$
Question 2
1 / -0

Velocity of light in a medium is $$1.5\times 10^8 m/s$$. Its refractive index will be

A
$$8$$

B
$$6$$

C
$$4$$

D
$$2$$

Solution

$$c$$=$$3 \times 10 ^{8} m/s^{-1}$$........Speed of light in vaccum
$$v$$=$$1.5 \times 10 ^{8} m/s^{-1}$$........Speed of light in medium
$$\mu =\dfrac {c}{v}=\dfrac {3\times 10^8}{1.5\times 10^8}=2$$
Question 3
1 / -0

If the speed of light in vacuum is $$C\ \ m/sec$$, then the velocity of light in a medium of refractive index $$1.5$$ is

A
$$1.5\times C$$

B
$$C$$

C
$$\dfrac {C}{1.5}$$

D
Can have any velocity

Solution

Spped of light in vacuum $$=C$$ m/s
Refrective index of medium $$\mu=1.5$$
Velocity of light in any medium having refrective index $$\mu$$, $$v=\dfrac C\mu$$
On putting the value of $$\mu$$, $$v=\dfrac C{1.5}$$

Option D.
Question 4
1 / -0

On a glass plate a light wave is incident at an angle of $$60^o$$. If the reflected and the refracted waves are mutually perpendicular, the refractive index of material is

A
$$\dfrac {\sqrt 3}{2}$$

B
$$\sqrt 3$$

C
$$\dfrac {3}{2}$$

D
$$\dfrac {1}{\sqrt 3}$$

Solution

From figure
$$ < i=60^o, < r=30^o$$
so $$\mu =\dfrac {\sin 60}{\sin 30}=\sqrt 3$$
Question 5
1 / -0

Refractive index of glass is $$\dfrac {3}{2}$$ and refractive index of water is $$\dfrac {4}{3}$$. If the speed of light in glass is $$2.00\times 10^8\ m/s$$ , the speed in water will be

A
$$2.67\times 10^8 m/s$$

B
$$2.25\times 10^8 m/s$$

C
$$1.78\times 10^8 m/s$$

D
$$1.50\times 10^8 m/s$$

Solution

As we know,
$$\mu=\dfrac{c}{v}$$
$$\mu\propto \dfrac {1}{v}$$ where $$\mu$$
is refractive index of medium , $$c$$ speed of light in vaccum and $$v$$ is speed of light in medium $$\Rightarrow \dfrac {\mu_g}{\mu_w}=\dfrac {v_w}{v_g}\Rightarrow \dfrac {3/2}{4/3}=\dfrac {v_w}{2\times 10^8}$$
$$\Rightarrow v_w =2.25\times 10^8 m/s$$
Question 6
1 / -0

A convex lens

A
Converges light rays

B
Diverges light rays

C
Form real images always

D
Always forms virtual images

Solution

A convex lens converges ray of light coming from an object to form a real and inverted image provided object is not located in front of Focal Length($$F$$) of the lens. If object is located in front of $$F$$ then image formed is virtual and magnified.

Hence, only option A is correct.
Question 7
1 / -0

When a ray of light passes through the second optical medium with a change in the angle, the phenomenon is known as:

A
Reflection of light

B
Absorption of light

C
Refraction of light

D
None of these

Solution

The bending of rays of light after passing through one medium to another is known as refraction.
A light ray traveling obliquely from a denser medium to a rarer medium bends away from the normal. A light ray bends towards the normal when it travels obliquely from a rarer to a denser medium.
Question 8
1 / -0

Which of the following event is not related to refraction of light ?

A
The bottom of water filled bowl appears raised.

B
Appearance of sun before sun rising and after sunset

C
Formation of image by mirror

D
Twinkling of stars

Solution
Question 9
1 / -0

Which of the following materials has maximum optical density?

A
Glass

B
Water

C
Pearl

D
Diamond

Solution

Diamond
Diamond has the highest refractive index of $$2.42$$. The larger the refractive index of a medium, the greater is its optical density.
Question 10
1 / -0

The magnification of plane mirror is always ...............

A
More than 1

B
1

C
Less than 1

D
Zero

Solution

1
Since the size of the image formed by a plane mirror is equal to the size of the object, its magnification is always 1.

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Light Reflection and Refraction Test - 67

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Light Reflection and Refraction Test - 67

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Question 1

$$0.4\ cm$$ away from the mirror

$$0.4\ cm$$ towards the mirror

$$0.8\ cm$$ away from the mirror

$$0.8\ cm$$ towards the mirror

Solution

Question 2

$$8$$

$$6$$

$$4$$

$$2$$

Solution

Question 3

$$1.5\times C$$

$$C$$

$$\dfrac {C}{1.5}$$

Can have any velocity

Solution

Question 4

$$\dfrac {\sqrt 3}{2}$$

$$\sqrt 3$$

$$\dfrac {3}{2}$$

$$\dfrac {1}{\sqrt 3}$$

Solution

Question 5

$$2.67\times 10^8 m/s$$

$$2.25\times 10^8 m/s$$

$$1.78\times 10^8 m/s$$

$$1.50\times 10^8 m/s$$

Solution

Question 6

Converges light rays

Diverges light rays

Form real images always

Always forms virtual images

Solution

Question 7

Reflection of light

Absorption of light

Refraction of light

None of these

Solution

Question 8

The bottom of water filled bowl appears raised.

Appearance of sun before sun rising and after sunset

Formation of image by mirror

Twinkling of stars

Solution

Question 9

Glass

Water

Pearl

Diamond

Solution

Question 10

More than 1

1

Less than 1

Zero

Solution

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